The invention relates to an aerodynamic device suitable to be fastened under and to extend downwards from a vehicle, especially a vehicle having a substantially vertical front face such as a truck for example. The invention also relates to a vehicle comprising an aerodynamic device.
For many years, attempts have been made to improve vehicle efficiency. One factor in an efficient design is the aerodynamic characteristics of a vehicle. The air drag of a vehicle and especially of an industrial vehicle such as a truck is one of the factors that has a direct impact on fuel consumption. Therefore, in a general trend towards rare and expensive energy—whether fossil or not—, aerodynamics is one of the key issue in an efficient vehicle.
One problem with the current industrial vehicles is the drag generated by air flowing under the vehicle. Indeed, when the vehicle is in motion in the forward direction, an air flow passes under the vehicle, roughly from front to rear, with a possible tilt with respect to the longitudinal direction in case of lateral wind. This air flow tends to cause turbulence around the vehicle wheels Therefore, such an air path is not favourable from an aerodynamics perspective insofar as it increases the vehicle drag coefficient and, consequently, generates high fuel consumption.
It therefore appears that there is room for improvement in vehicles aerodynamics, especially under the vehicle.
It is desirable to provide an aerodynamic device which improves aerodynamics under the vehicle.
According to a first aspect of the invention, by mounting under a vehicle an aerodynamic device having dimensions adapted to the vehicle dimensions, and by positioning it appropriately, it is possible to deflect and canalize air flowing rearwards under the vehicle away from the vehicle wheels. Therefore, the drag under the vehicle is decreased, especially the drag due to the wheels.
Indeed, on the one hand, part of the incoming air is made to enter the channels provided between the central spoiler and the lateral spoilers. Because the channels are convergent rearwards and due to the positioning of their axis, this air flow is accelerated and canalized rearwards, substantially longitudinally. As a result, at each channel rear end, there is obtained a narrower and fairly strong air flow which can efficiently be directed in the appropriate direction. The overall result of this arrangement is that the air flow passing under the trucks is deviated substantially longitudinally, whatever the direction of the incoming air flow, which allows the wheels not to be on the air path. After the air flow has come oat of the channels, its direction cannot be controlled anymore. However, owing to the acceleration provided by the channels, the air flow tends to follow the direction it has been given on a longer way rearwards. This greatly limits the amount of air flowing towards the wheels.
On the other hand, the aerodynamic device can furthermore be designed so that another part of the incoming air flows along the outer side walls of the lateral spoilers or even is diverted outwards, so as to limit the drag to the vehicle wheels.
The invention therefore makes it possible to greatly improve the air path below the level of the vehicle floor—i.e. both sander the vehicle and around the vehicle—and consequently to lower the vehicle aerodynamic drag and decrease the fuel consumption.
Allowing air to flow under the vehicle, along an improved path, also ensures stability of the vehicle as compared to front aerodynamic devices preventing air from flowing under the vehicle.
By “a channel having a substantially longitudinal axis” is meant that the channel axis and the longitudinal direction can form a slight angle, typically lower than 10°, and preferably lower than 5°. The channel can be oriented slightly outwards, provided it makes it possible for the canalized airflow not to be directed towards the vehicle wheels. The “channel axis” is defined as the bisecting line of a sector formed by the side walls of two contiguous spoilers, e.g the sector formed by the inner side wall of the right lateral spoiler and the right side wall of the central spoiler, or by the inner side wall of the left spoiler and the left side wall of the central spoiler.
The inner side wall of a lateral spoiler and the corresponding side wall of the central spoiler are not necessarily symmetrical with respect to a longitudinal axis. As regards the lateral spoilers, they are preferably substantially identical, this not being limitative.
In the operative position of the aerodynamic device, the upper edges of the front walls of the central spoiler and lateral spoilers can be arranged substantially in a same transverse and vertical plane.
According to an embodiment, the channel side walls form together an angle which points rearwards and which ranges from 5° to 50°, preferably from 10° to 40°, for example around 30°. This makes it possible to direct airflow in the proper direction under the truck.
According to an embodiment, the channel width, at the channel front end, ranges from 80% to 170% of the lateral spoiler greatest width, preferably from 100% to 150%.
According to an embodiment, the spoilers lower parts are capable of being elastically delbrmed by a rigid element such as an obstacle or a pavement. However, the spoilers are rigid enough not to be deformed by the incoming air flow, in normal conditions. This feature prevents the spoilers from being damaged in case they hit such a rigid element. For example, the spoilers lower parts—or the whole spoilers—can be made of a soft plastic material. In case of a shock, the damaged spoiler(s) can be replaced.
Besides, the thickness of at least one spoiler can decrease from its upper edge towards its lower edge. This feature can be used to make the spoilers lower parts elastically deformable as previously explained.
According to an embodiment, each side wall and the front wall of the central spoiler form an angle ranging from 80° to 150°, preferably from 90° to 120°, for example around 110°. More generally, said angle ranges from a minimum to a maximum value, with the minimum value being 80°, preferably 90°, more preferably 95°, and the maximum value being 150°, preferably 140°, preferably 120°, and more preferably 110°.
As regards the central spoiler length—along the longitudinal direction—from its front end towards its rear end, it can range from 50 to 200 mm, preferably from 50 to 160 mm. This feature ensures that air flow is properly directed and that the aerodynamic device does not degrade aerodynamics.
Below the minimum value, efficiency is not optimum. Above the maximum value, the central spoiler drag is too high; moreover, in case of lateral wind, the surface area hit by incoming air is too high, which decreases the aerodynamic device efficiency.
Besides, the central spoiler height—along the vertical direction—can range from 30 to 150 mm. Below 30 mm, aerodynamics benefit is negligible, while above 150 mm, the ground clearance of the vehicle is not high enough.
According to an embodiment, the inner side wall of each lateral spoiler and the longitudinal direction form an angle ranging from 0° to 50°, preferably from 5 to 20°, each inner side wall being angled inwards. More generally, said angle ranges from a minimum to a maximum value, with the minimum value being 0°, preferably 5°, more preferably 10°, and the maximum value being 50°, preferably 45°, and Inure preferably 20°. This makes it possible to direct air so that it does not hit the wheels.
The lateral spoiler height—along the vertical direction—can range from 30 to 250 mm. Below 30 mm, aerodynamics benefit is negligible, while above 250 mm, the ground clearance of the vehicle is not high enough. The height of the lateral spoiler may increase front the front part to the rear part of the spoiler.
According to an embodiment, the outer side wall of each lateral spoiler has a front portion the height of which increases from front to rear, and a rear portion having a substantially constant height.
According to a second aspect, the invention further relates to a vehicle with an arrangement of the spoilers, wherein the invention provides a kind of aerodynamic shield which, viewed in a horizontal plane, has a shape substantially corresponding to the vehicle shape. This aerodynamic shield (i) deflects part of the incoming air outwardly along the lateral spoilers and (ii) only allows the incoming air to flow under the vehicle through the dedicated channels, which enables an efficient control on the air flow direction.
According to an embodiment, the outer side wall of each lateral spoiler extends rearwards substantially up to the corresponding first wheel. Owing to this feature, there is no gap, or no significant gap, between the lateral spoiler and the corresponding first wheel, which prevents laterally directed air from hitting the opposite first wheel, and greatly improves the vehicle aerodynamics.
The plane of the upper edges of the front walls of the central spoiler and lateral spoilers can be located rearwards from the vehicle front face, at a longitudinal distance ranging from 0 to 30% of the longitudinal distance between the vehicle front face and the first axle, preferably from 0 to 15%. Owing to this feature, the invention makes it possible to canalize the incoming air flow substantially from the vehicle front face, thereby improving the aerodynamics. In practice, the longitudinal distance between the plane of the upper edges of the spoilers front walls and the vehicle front face can be around 5-10 cm.
According to an embodiment, the spoilers are fastened onto the front underrun protection (FUP). Other implementations can however be envisaged.
According to an embodiment, the channel width, at the channel front end, ranges from 0.06 L to 0.24 L, where L is the vehicle width, preferably from 0.08 L to 0.18 L. Below the width minimum value, it is difficult to make air enter she channels. Above the maximum value, the air flow at the channel rear end is too wide and not strong enough: as a result, the air flow cannot be efficiently canalized and adequately directed away from the wheels. In concrete terms, for a truck having a width of 2.5 m, the channel width, at the channel front end, can range from 150 to 600 mm, preferably from 200 to 450 mm.
According to an embodiment, the angle formed between the inner side wall of a lateral spoiler and a functional line ranges from 0° to 45°, preferably from 5° to 15°, the functional line being defined as the substantially horizontal line joining the rear edge of the inner side wall of the lateral spoiler and the point of the corresponding first wheel which is located inwards and most forward. Since, rearwards from the channel rear end, the air flow tends to get closer to the corresponding first wheel, this feature aims to ensure that the air flow does not hit said wheel. Furthermore, with this feature, the front area of the aerodynamic device is not too high, which would result in a less important gain from the aerodynamics point of view.
Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.